Les Paul jun. and "vintage wiring"

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http://www.lespaulforum.com/forum/showpost.php?p=2108835&postcount=32
I did not know the values of the pots in my 60 TV. This posting gave me the information: The vol-pot is 500k, the tone-pot is 250k.

That seems to be quite unusual. But the more I think of it, the more it makes sense to me considering the important fact, that the "vintage wiring" was used. Here is a pic of the contol cavity of my TV (pic made by Tom).



You see "vintage wiring": The cap is soldered to the middle lug of the vol-pot.

I always wondered why my TV reacts so "magical" when reducing the volume.
When I first played my 1960 LP TV in the 80s I was struck by the behaviour of the volume pot.
I had expected the sound to become a little bit "dull" as it happens with all the other guitars when lowering the volume.
But this did not happen. The sound was still there - bright and belly.
I call this "magical".

Until recently I thought this to be a speciality of the "old P90" Pickup.
Now that I know the values of the pots, I see more clearly now.

Please let me share my theoretical ideas about the tonal effect of a vol.-pot with 500k and a tone-pot with 250k in addition with "vintage-wiring":

The combination of the capacitor and the tone pot is called a "filter".
It consists of a capacitor and a resistor.
The filter affects the "resonance-frequency" of the pickup.
It flattens the peak of the resonance-frequency and also decreases the location (in Hz) of this peak.
If the tone-pot is "10" the effect of the cap is minimum, because ground (GND) is "far away". The resonance frequency of the PU is not affected much.
If the tone pot is "1" the effect is maximum because GND is directly connected to the cap, in other words the cap is in paralled with the PU. You have a "woman tone".

(Later we discuss, what happens at "5".) Let us first assume the vol.-pot is "10":
Electronically now there is no difference between "modern" and "vintage" wiring. The PU is directly connected to the output jack.
The sound of the PU is not affected by the vol.-pot. (Yes, I know, the 500k of the volume-pot to GND are still there and this means something, but we can neglect that fact here.)
Let us assume the tone-pot is "10". Can we say, the sound now is also not affected? No.
The sound IS still affected, because the filter is still there, although the filter is not so "strong".
As the effect ist small, the guitar is "bright". BUT:
A little dampening effect is there: you have the cap and a resistor between the hot PU wire and GND.

I have learned that the effect of the filter in the LP jun. is "bigger" than for example in a LP Standard.
In a LP jun. at "10" the cap is only 250 kOhms away from GND.
In the LP Standard at "10" the cap is 500 kOhms - much more - away from GND.

That means:
The Gibson designers wanted the P90 to be "tamed", they wanted more "taming" for the P90 than for the humbucker.
(Interesting: The word "to tame" and the german word "zähmen" are the same old words.)
Why: Because the P90 is a "beast", a "treble-monster" - like the ones in the Stratocaster.
Such a "wild horse" has to be "tamed" even when all the knobs are at "10".
This "taming" is done with the 22nF cap and ONLY 250 kOhms to GND.

Has anybody tried to play a LP jun. with the filter disconnected?
I have not done that. I want to leave the soldering points in my TV original.
But I can assume: The sound of a P90, when (directly) plugged into a tube amp with at least 1 MegOhms input-impedance will sound "harsh". Biting treble that will damage your ear....
So what we call the "sound of the P90" is not the pickup alone.
Even all knobs at "10", the sound is a mixture of the PU and the filter (22 nF cap and 250 kOhms to GND).

Now I describe, the MAGIC that happens, when you keep the tone-pot at "10" and lower the vol-pot to "5".
All the text up to now was written for that purpose:

As I said before, at "10" there is no difference between "modern" and "vintage" wiring.
BUT: If you turn the vol.-pot to maybe "5", the filter becomes and acts different.
Assuming the vol.-pot is linear, then we have in "vintage wiring" 250k Ohms between the PU and the input of the filter.

Electronically the filter consists now
1. of the 250 kOhms of the vol.-pot
2. of the 22nF cap
3. of the 250 kOhms of the tone-pot.

Electronically it is not important what is where in the filter chain.
So we have: the 22nF cap and a (250+250=) 500 (!!) kOhms resistor.
Now the filter is EVEN MORE SMALLER than "normally" (with both pots at "10")!!
(This does not happen in modern wiring, because the filter is connected directly to the hot PU wire.)

That means: "Vintage wiring" is a great design!
As you turn down the volume, the guitar even becomes brighter!

So why did the Gibson designers use this feature?
They used this feature because of another effect, that I haven't explained yet:
Every PU becomes a little bit "dull" when reducing the volume on the guitar.
This is normal. The high impedance PUs react "stressed" on the "burden" of the volume pot.
"Vintage wiring" and the intelligent use of the mentionend values of the pots in the LP jun. COMPENSATE this "stress".
This technology provides the magical "bright" and "belly" sound when reducing the volume on the LP jun.

Fred

Hi! Almost all single P-90 pickups and Melody Makers were wired with a 500K audio taper Volume and a 250K audio taper for Tone. The 250K reduces some of the highs and I think makes the .022 cap work a bit smoother. Your guitar looks stock on the wiring. I don't think anyone has been in there. Since you obviously love the way it sounds, then leave it alone and just enjoy playing it!!
Nice Jr.!!

.

Very interesting post, thanks for sharing.

Thanks for your profuse comments and observations! :salude

So, how did Gibson wire the LP Special, with 2 P-90s? did they still use 250K pots for the tone controls or did they stick with 500K pots, since you had the option of the neck pickup for a "mellow" tone?

Uncle Gary said:

So, how did Gibson wire the LP Special, with 2 P-90s? did they still use 250K pots for the tone controls or did they stick with 500K pots, since you had the option of the neck pickup for a "mellow" tone?

Click to expand...

Good question. I would like to add another - I am looking at a 57 Junior and it appears the cap is soldered to the outer lug, not the middle like in Fred's pic (see below). So which configuration is more common or is it year specific? And Fred would you care to speculate as to how that affects the tone?

Uncle Gary said:

So, how did Gibson wire the LP Special, with 2 P-90s?

Click to expand...

1956

Red Rocket said:

Good question. I would like to add another - I am looking at a 57 Junior and it appears the cap is soldered to the outer lug, not the middle like in Fred's pic (see below). So which configuration is more common or is it year specific? And Fred would you care to speculate as to how that affects the tone?

Click to expand...

I can't answer as to which configuration is the most common...but the cap-to-the-outer-lug would give you the more typical "tone gets muddy as you turn down the volume".

Jim Jones said:

I can't answer as to which configuration is the most common...but the cap-to-the-outer-lug would give you the more typical "tone gets muddy as you turn down the volume".

Click to expand...

Thanks Jim. Expert opinion needed from you dealers and old hands - If you moved the cap over to the middle lug and disturbed what were previously untouched original soldering points, would that greatly affect the value?

Red Rocket said:

I am looking at a 57 Junior and it appears the cap is soldered to the outer lug, not the middle like in Fred's pic (see below). So which configuration is more common or is it year specific? And Fred would you care to speculate as to how that affects the tone?

Click to expand...

No, Red Rocket, I do not think that your Junior is different. The cap is soldered to the middle lug of the volume pot. In your pic the volume pot is on the left side. You see the pickup cable coming through the hole from the left. The inner "hot" wire is soldered at the outer lug of the volume pot, you can also say: at the "input" of the volume pot. The (extra plastic shielded) cable to the output jack is soldered to the middle lug of the volume pot. You see very clearly that the cap (the input of the filter) is soldered to this middle lug. This is vintage wiring. It provides all the advantages I explained it in my first post.

The pic of the control cavity of Tom's 1956 Special is not easy to interpret. You also see the volume pots on the left side. Much is hidden there by the cables. But I am quite sure that the "upper" cap is not soldered to the "input" of the "upper" volume pot. So this is also "vintage wiring". Still we do not know what the values of the pots are. I would expect the same 500k - 250 k couple - just like in a junior.

Finally here is my recommendation for LP Standard users:
As these have 500 k volume pots and 500 k tone pots originally, how can we provide the advantages of the intelligent Junior design to these guitars?

First: The biggest and most easy mod is to change from modern to vintage wiring. Just desolder the cap from the outer lug and solder it to the middle lug.

Second (and new): Since we do not want to change the "filter-unit", the tone pot must be kept 500k. If you now change the value of the volume pot to 1 Meg Ohms, you are on your way. Assuming a linear pot, at "5" you have 500 k + 500 k in the filter. The cap is now 1000 kOhms "away" from GND. The PU will be brighter than normally. I have not tested this, but I have seen german (Hofner) guitars with 1 Meg pots.


Fred

Fred Hullerum said:

No, Red Rocket, I do not think that your Junior is different. The cap is soldered to the middle lug of the volume pot. In your pic the volume pot is on the left side. You see the pickup cable coming through the hole from the left. The inner "hot" wire is soldered at the outer lug of the volume pot, you can also say: at the "input" of the volume pot. The (extra plastic shielded) cable to the output jack is soldered to the middle lug of the volume pot. You see very clearly that the cap (the input of the filter) is soldered to this middle lug. This is vintage wiring. It provides all the advantages I explained it in my first post.Fred

Click to expand...

I see what you mean now, your eyes are better than mine (damn computer screens). I was looking at the wrong lead.

Thanks for the rest of your post too. :3zone